Seed development and seed shedding in North Italian ecotypes of Lolium multiflorum

Seed development and seed shedding were studied in seven populations of Lolium multiflorum. Five of these populations were from the North Italian Plains, two from the Piedmont area and three from the Lombardy region. The remaining populations were Delecta, a variety derived from ecotypes from the Lombardy Plain, and RvP Lemtal. Seed shedding was greatest in the three ecotypes from the Lombardy Plain and lowest in RvP Lemtal. The two ecotypes from the Piedmont Plain, and Delecta, gave intermediate values. Moisture loss during ripening was greatest in the Lombardy ecotypes but there were no differences in the time taken to reach maximum 1000-seed weight. Germination values had reached a maximum 27 d after anthesis in all populations. It is suggested that the North Italian ecotypes, or varieties derived from them, should be harvested by direct combining at a moisture concentration of 450 g kg^-1 (≡45%) to obtain the maximum weight of germinable seed.     

The effect of time of harvest on seed production of three red clover cultivars

Small plots of red clover cv. Sabtoron, S123 (diploids) and Hungaropoly (tetraploid) were harvested for seed production at two-week intervals from 19 August to 17 October inclusive in 1981, inflorescence appearance rate, bee density and components of yield having been monitored throughout the summer. Inflorescence appearance rate reached a maximum at the end of July/early August for Hungaropoly and Sabtoron and during mid-August for S123. Bee density followed a similar pattern. Florets and seeds per inflorescence and 1000-seed weight decreased as flowering progressed except during the first three weeks in July. Potential seed yield was calculated from the components of yield for the harvests taken on 3 and 18 September. Losses in seed yield (difference between actual and potential) up to and during harvesting, threshing and cleaning were lower in the tetraploid cultivar (27–39%) than the diploid cultivars (35–l55%). Each cultivar had an optimum harvest time before which yield was affected by immature seeds and beyond which it was adversely affected by shedding of inflorescences and seeds and sprouting of seeds on the inflorescences. The optimum time to harvest Sabtoron was early September, Hungaropoly early to mid-September and the late flowering cultivar S123 mid-September when less than 4% of the inflorescences were still unripe. Seed yield and inflorescences per unit area were lower in the tetraploid cv, Hungaropoly (maximum 542 kg ha⁻¹) than diploid cv. Sabtoron and S123 (864 and 897 kg ha⁻¹ respectively) although the tetraptoid had heavier seeds. It is concluded that the optimum time to harvest red clover for seed production is about three or four weeks after the end of the period of rapid inflorescence production and that this coincides with the time when only a small proportion of unripe inflorescences remain.     

Seed variation among annual ryegrass cultivars in south-eastern USA and the relationship with seedling vigour and forage production

Abstract Annual ryegrass (Lolium multiflorum Lam.) is grown on more than one million ha in the south‐eastern USA each year. Recommended and actual seeding rates vary substantially within the region. The objective of this study was to evaluate variation in seed weight, germination, seedling vigour and seasonal yield performance among annual ryegrass cultivars. During 1997, 1998 and 1999, seed from fourteen commercial cultivars was weighed and germinated to determine numbers of pure live seed (PLS) m^?2 before yield evaluation at four locations. Seed from ten cultivars was planted at 0·7 and 2·0 cm depth in a greenhouse study to evaluate relative seedling vigour. Cultivar mean single‐seed weight ranged from 2·4 to 4·8 mg in 1997, 1·8 to 4·5 mg in 1998, and 2·6 to 4·6 mg in 1999. Seed germination ranged from 78·8% to 98·0% in 1997, 82·3 to 98·3% in 1998 and 77·8 to 98·3% in 1999. Seed number, PLS m^?2, ranged from 675 to 1289 in 1997, 710 to 1550 in 1998, and 717 to 1179 in 1999. Among the ten cultivars evaluated for seedling vigour, seedling weight differed between planting depths and a significant cultivar by year interaction was observed. Seedling weight was highly correlated with seed weight at each seeding depth. The effect of increasing number of PLS m^?2 on subsequent yield performance, although small, was consistently negative. These results indicate that target plant populations may be obtained more economically by adjusting seeding rates for seed size differences among cultivars and seed lots of annual ryegrass.     

Differences in development of common bean (Phaseolus vulgaris L.) crops and pod fractions within a crop: I. Seed growth and maturity

Two experiments with common bean cultivars Rosecoco and Mwezi Moja aimed at increasing insight into differences in development with time of seeds from pods of different earliness classes within a crop. Pods were divided into three earliness classes (early, medium, and late) in relation to the fourth class, the overall crop. In all pod classes, cultivars and seasons, seeds achieved physiological maturity (PM: maximum dry weight) when fresh weight was at its maximum. PM was achieved at 58% seed moisture content in seeds from all pod classes and cultivars. Seeds from earlier pods tended to reach PM earlier than those from other classes. The time when seeds developed their final red purple colour pattern was a reasonable indicator of PM, though not completely accurate. Harvest maturity (HM: 20% seed moisture content) was reached earlier in earlier pods in cv. Rosecoco, but the timing was the same for all pod classes in cv. Mwezi Moja. The period for seeds to dry down from 58 to 20% moisture content was longer in seeds from earlier pods in cv. Mwezi Moja, but not in cv. Rosecoco. The course of decline in moisture content between 58 and 20% differed between pod earliness classes, but was not systematically affected by earliness. The timing of seed development in the overall crop could be explained by the timing of seed development in pods of different earliness classes. Relationships among seed moisture content and seed or pod colour in whole crops differed from those in pods of individual earliness classes.     

Spring defoliation of white clover seed crops. 2. Potential harvestable seed yield and seed yield components of contrasting white clover cultivars

The effects of different spring defoliation managements on potential harvestable seed yield and seed yield components of three contrasting white clover cultivars were assessed. The small-leaved cv. S184 produced more but smaller inflorescences than the large-leaved cv. Olwen and Menna, a medium-leaved cultivar. Cultivar Olwen, however, produced more ripe and brown (nearly ripe) inflorescences with more florets, seeds per floret and a higher seed yield per ten inflorescences than the other cultivars. Potential harvestable seed yield and individual seed yield components were only influenced by defoliation after bud emergence, as defoliation before bud emergence had no effect on seed yield components. Defoliation after bud emergence had a similar effect on all cultivars: the number of ripe inflorescences was unaffected by defoliation but the number of brown and therefore harvestable (ripe + brown) inflorescences was highest following defoliation three weeks after bud emergence. Florets per inflorescence, seed per floret, 1000 seed weight, seed yield per ten inflorescences and potential harvestable seed yield were not influenced by defoliation after bud emergence. Season had a significant effect on seed yield components and influenced the effect of defoliation treatments, emphasizing the importance of climate in white clover seed production. The results are discussed in relation to the spring defoliation of white clover seed crops, harvesting techniques and the provision of guidelines for optimizing seed yield.     

Impact of seeding rate on annual ryegrass performance

Annual ryegrass (Lolium multiflorum Lam.) is a primary forage resource for livestock producers throughout the south‐eastern USA during the winter‐growing season. It is important for livestock producers to begin grazing annual ryegrass as early as possible and any management practices maximizing early season production could be beneficial. To assess the impact of seeding rate on subsequent yield, yield distribution, quality, seedling density, and end‐of‐season plant and tiller density, a 2‐year study was initiated at four locations in Louisiana. Three annual ryegrass cultivars, varying in seed size, were established at four seeding rates based on pure live seed (PLS) rates of 400, 800, 1200 and 1600 PLS m^?2. There was no advantage in total yield from increasing seeding rates beyond 800 PLS m^?2. However, first‐harvest yields increased from 360 to 930 kg dry matter (DM) ha^?1 as seeding rate increased from 400 to 1600 PLS m^?2. Crude protein and neutral‐detergent fibre concentrations, and in vitro DM digestibility, were not affected by seeding rate. Seedling density and end‐of‐season plant numbers increased as seeding rate increased. However, stems per plant decreased as seeding rate increased, indicating compensatory tillering for the reduced plant numbers observed at the lower seeding rates. These results indicate first‐harvest yield can be increased by planting at higher seeding rates but total yields are not increased.     

吉林省不同年代大豆品种遗传改良过程中某些农艺性状的变化

两年来对吉林省1923～2005年生产上主推16个大豆品种的生物量、产量、收获指数以及种子蛋白质、脂肪含量的研究表明：大豆植株的生物量从苗期到R6期逐渐增加，到R6期达到最大值，然后下降，老品种比现代品种下降速度快。大豆品种的生物量、产量和收获指数均随育成年代呈线性增加，其中产量和收获指数平均每年分别增加14.84kg/hm2（1.29%）和0.09 %。种子脂肪含量随育成年代增加，平均每年增加0.87%；而蛋白质含量随年代降低，平均每年下降1.52%。产量与生物量和收获指数呈显著正相关(P<0.05)；与种子脂肪含量呈正相关，与蛋白质含量呈负相关，但不显著。本文结果表明，大豆育种工作者以高产为选择目标的同时使生物量和收获指数得到提高。生物量和收获指数可以作为高产品种选育的指标。     

Seed yield,oil content and fatty acid composition of Oenothera biennis L. affected by harvest date and harvest method

Evening primrose (Oenothera biennis L.) has become a subject of agricultural interest because of the potential market for γ-linolenic acid, which is useful in medicine and nutrition. O. biennis has good potential for agricultural production, but due to its indeterminate growth it can not be harvested at once as seed are formed and ripened heterogeneously. As a result there is high seed wastage due to shattering. Field experiments were carried out to verify the influence of the harvest time (early, middle and late) and harvest method (conventional harvest method, defoliation by herbicide and defoliation by flame) on the seed yield, seed yield components, oil content, fatty acid composition and protein content of the O. biennis L. cv. “Anothera”. From the results of the three harvest times in the autumn-sown experiment, a significant influence on seed yield was observed in the late harvest. Of all the three harvest times in the spring experiments, not showed any significant influence on seed yield. However, the harvest method did produce a significant influence on seed yield in the first spring experiment. Different harvest times did not have significant influence on oil content except the second spring trial. The harvest method led to significant differences on the oil content when the plants were sown in autumn. In the second spring experiment seed protein content was significantly influenced by harvest time. In all experiments, the content of γ-linolenic acid (GLA) was influenced by harvest time. Based on obtained results, it can be concluded that 75–80 and 100 days after flowering could be recommended as harvest times for spring and autumn-sown O. biennis L. cv. “Anothera” in Germany, respectively. Desiccation as a harvest technique in some cases tended to influence on seed yield, PDM, SDM, oil content, stearic acid, oleic acid and linoleic acid. Defoliation by herbicide was more effective than those of flame in our experiments.     

Effect of seed crop management on potential seed yield of contrasting white clover varieties

An experiment is described in which the effects of different spring managements on the potential seed yield and seed yield components of three white clover cultivars of contrasting leaf types were assessed. Cv. S184, the small-leaved variety, produced more but smaller inflorescences than CVS Olwen, a large-leaved variety, or Menna, a medium-leaved variety. However, cv. Olwen, produced inflorescences with more florets, seeds per inflorescence and a higher seed yield per ten inflorescences than the other cultivars. Both potential seed yield and the individual yield components were influenced by management. Cv. Olwen produced more inflorescences and a higher potential seed yield under a cutting system than under grazing systems, which reduced the number and size of the inflorescences. Cvs S184 and Menna were less influenced by management system and performed similarly under cutting and grazing. The highly significant relationship between the number of ripe inflorescences and potential seed yield showed clearly that high seed yields are only achieved if the crop is harvested when the number of ripe inflorescences is at a maximum. The relatively short duration of the period of maximum ripe inflorescences emphasized the importance of determining the correct harvesting date, although weather conditions also play an important part in deciding when to harvest. Florets per inflorescence, seed set and 1000 seed weight remained relatively constant over the harvest period, and were not influenced by harvest date. The results are discussed in relation to the management of white clover seed crops and the importance of climatic conditions during seed production.     

Optimum time of combine harvesting for amenity grasses grown for seed

The relationships between, and changes in moisture content, 1000-seed weight, germination percentage and seed yield were determined from anthesis onwards in ten amenity grasses in 1975. These relationships were used to indicate the optimum date for combine harvesting and to give some indication of the consequences which follow if harvest was not carried out at this stage. In all species seed moisture content declined, and 1000-seed weight and germination increased to a maximum value, during ripening.     

山西玉米子粒含水率与机械粒收收获质量的关系分析

2013～2014年在山西忻州开展适宜机械粒收品种的筛选和机械粒收技术示范,探讨玉米不同品种子粒含水率与子粒破碎率、杂质率以及产量损失率之间的关系。结果表明,破碎率、杂质率以及产量损失率均与子粒含水率存在显著正相关,子粒水分是影响机械粒收质量的重要因素。筛选子粒含水率低、产量水平高的瑞普959、德美亚3号、瑞普908和M753推荐为当地适宜粒收品种。     

Biomass distribution,maturity acceleration and yield in drought-stressed common bean cultivars

Common bean (Phaseolus vulgaris L.) is an important food crop grown under rainfed conditions in Latin America where drought is a major limiting factor for production. The objective of this study was to assess the role of phenological adjustment and shoot biomass distribution on seed yield of drought-stressed common bean. Four cultivars differing in growth habit, gene pool origin, and contrasting responses under drought, were tested during 2001 at two locations in Mexico: Cotaxtla, Veracruz (lowlands) where the effect of terminal drought (TD) (end-of-season) was evaluated, and Texcoco, State of Mexico (highlands), where the effects of intermittent and terminal drought were evaluated. Seed yield, plant shoot biomass, and days to flowering and to physiological maturity were recorded. Leaf relative water content (RWC) was recorded after the onset of the intermittent drought (ID) treatment in Texcoco. The drought intensity index was 0.37 in Cotaxtla compared to 0.49 and 0.58 under TD and ID, respectively in Texcoco. Days to flowering and to physiological maturity showed a negative and significant relationship with seed yield. Under drought stress, a significant reduction in the harvest index was observed in susceptible cultivars. All cultivars showed higher values of shoot biomass accumulation, pod and seed number, seed weight and RWC at the basal nodes of the plant across locations and moisture treatments. Cultivar Pinto Villa exhibited the highest biomass accumulation and seed yield across treatments and locations. Significant reduction in number of days to maturity was observed under drought, mainly in resistant cultivars, Pinto Villa and G4523. Maturity acceleration, coupled with a high seed filling rate, contributed to lessen the impact of drought stress in resistant common bean cultivars.     

A comparison of seed harvesting methods for perennial ryegrass treated with the growth retardant paclobutrazol

Methods of harvesting seed of perennial ryegrass cv. S24 treated with the growth retardant paclobutrazol applied at spikelet initiation at a rate of 2.0 kg active ingredient ha⁻¹ were examined in 1982. The greatest seed yield (2202 kg ha⁻¹) was obtained from swathing the crop at 35% seed moisture content and combining 2 days later, but this was not significantly different from that obtained from swathing at 48% seed moisture content or double direct combining at 35% seed moisture content. Seed yields from a single direct combining at either 35% or 25% seed moisture content were significantly lower than those of other treatments.     

宁夏宜机收玉米品种的初步筛选

2015～2017年在宁夏扬黄灌区和引黄灌区开展239品/次适宜机械粒收玉米品种筛选试验。通过综合比较品种丰产稳产性、收获时子粒含水率等指标,筛选出3个适宜扬黄灌区机械粒收玉米品种,分别为银玉137、ZH846和先玉335。与对照郑单958相比,推荐品种早熟2～6.5 d,子粒含水率降低1.6～5.3个百分点,产量增加1.9%～12.2%。筛选出5个适宜引黄灌区机械粒收品种,分别是农华213、迪卡519、辽单575、登海605和先玉335。与对照郑单958相比,推荐品种早熟2～8 d,子粒含水率降低3.8～4.8个百分点,产量增加6.3%～18.7%。     

Influence of stage of maturity on the nutritive value of Italian ryegrasses

The influence of harvesting date on the nutritive value of the Italian ryegrass cv. RvP from Belgium and of Bb 1277, an introduced ecotype from the Po valley, was investigated.
Ten clonally replicated genotypes of each population were grown as closely spaced plants and two ramets of each genotype harvested every 4 d for a period of 28 d after inflorescence emergence. Dry matter digestibility (DMD) was estimated and fibrosity index (FI) determined on both the leaf and stem fractions, and cellulose and lignin concentrations were determined on the stem fractions.
The nutritive value of the leaf in terms of both DMD and FI which was the same for both cv. RvP and Bb 1277 throughout the period of harvesting, was always higher and declined at a slower rate with increasing maturity than that of the stem. The stem of Bb 1277 declined in DMD and increased in FI and cellulose concentration at a significantly slower rate than cv. RvP. Significantly higher levels of DMD were detected in the stem of Bb 1277 for harvests 5 to 8 and significantly lower levels of FI and cellulose concentration from harvests 4 to 8. It was not, however, possible to detect any significant differences in stem lignin concentration. Dry matter yields increased throughout the period of harvesting and there were no significant differences between cv. RvP and Bb 1277.
The results are discussed in relation to the breeding potential of the high nutritive value of the Po valley ecotype Bb 1277 and the use of the DMD and FI determinations for selecting for improved herbage quality in Italian ryegrass.     

Effect of sowing date on the growth and seed yield of common bean (Phaseolus vulgaris L.) in highland environments

Evaluations of common bean cultivars in the highlands of Mexico indicated that land races from that region experience less reduction in seed yield and seed size in late sowings than do lines from other regions. Introduced materials are of interest as sources of increased disease and pest resistance and tolerance to edaphic constraints, however. To quantify effects of sowing date and determine possible underlying causes, germplasm of diverse origins was evaluated at two sites in the highlands using multiple sowing dates. In all trials, seed yield, seed weight, harvest index and canopy dry weight decreased with late sowings. Large effects of sowing date, cultivar and their interaction were found for the four traits. The possible importance of phenology per se and of weather conditions was first examined using regression analyses. Variation in seed yield, seed weight, harvest index and canopy dry weight was more closely associated with time to maturity than with time to flowering. Of three weather variables examined, minimum temperature during seed filling revealed the strongest relations with the four traits. Few interactions of any parameter with line were significant, indicating that the cultivars did not have a strong differential response to a specific weather condition such as night temperature. Simulation analyses comparing photoperiod-sensitive and day-neutral cultivars indicated that radiation and temperature explained part of the yield reduction with late sowings. Daylength also had an influence, however, even in the day-neutral cultivar. Given that phenology had a strong effect on yield and that its inheritance is better understood than that of other physiological traits, priority should be given to understanding the genetic basis of the response of cultivar phenology to sowing date in the region.     

吉林省西部地区滴灌条件下宜机械粒收玉米品种筛选

确定宜机械粒收的玉米品种是构建吉林省西部旱作补灌区玉米丰产增效技术模式的重要内容之一。2018年和2019年在吉林省西部地区开展滴灌条件下宜机械粒收玉米品种的筛选试验,测定38个玉米品种的收获子粒含水率和产量,并按玉米子粒含水率和产量水平采用双向平均法作图进行品种分类。结果表明,本研究初步筛选出5个滴灌条件下宜机械粒收玉米品种,分别是迪卡159、福莱77,稷秾108、吉农大889和优迪919。根据品种综合性状分析,吉农大889较优,其次为迪卡159,可以作为适宜吉林省西部滴灌条件下丰产高效栽培的推荐品种。     

Alfalfa (Medicago sativa L.) seed yield and quality under different forage management systems and irrigation treatments in a Mediterranean environment

Alfalfa (Medicago sativa L.) is widely grown as a forage crop due to its good quality characteristics and high adaptability. However, seed yield is generally considered to be of secondary importance and is characterized by fluctuating yields with often poor seed quality. A field experiment using five alfalfa cultivars (Equipe, Iside, Lodi, Robot, Romagnola) was carried out in 1995, 1996 and 1997 at Foggia (southern Italy) to evaluate the effects of four defoliation practices (H1: crop mown during early plant growth; H2: plant desiccation by chemical agent at the end of February; H3: crop mown at early flowering; H4: never cut) and two irrigation treatments (I: irrigation applied from April to beginning of seed filling; NI: non-irrigated control) on seed yield, seed yield components and seed quality (as determined by seed germination with and without accelerated ageing (AA)). The relationships between yield components (stems per m², pods per stem, seeds per pod, 1000-seed weight) were determined by path-coefficient analysis. Irrigation significantly increased seed yield; on average doubling the control yield over the three seasons. However, the potential seed yield (calculated from seed yield components) was, on average, five times the actual seed yield. The two mowing treatments produced consistently higher seed yields than either desiccated or untreated swards. Cultivar differences were evident for seed yield, with Equipe having the highest value (40% higher than the mean of the other cultivars). Irrigation improved the yield primarily because it led on average a greater than four fold increase in the density of stems (the most influential yield component). By contrast, seeds per pod and 1000-seed weight increased in the absence of irrigation. Defoliation treatments had little effect on stems per m², seeds per pod and seed weight, whereas pods per stem were reduced by desiccation. Path analyses calculated across irrigation treatments and years revealed that stems per m² had the largest positive direct effect on alfalfa seed yield under each harvest management (path-coefficient values ≥0.89), and its indirect effects on seed yield via other traits were negligible. Seed quality, as measured by germination percentage both before and after AA, remained relatively consistent across both defoliation and irrigation treatments and cultivars, but was anomalously low in the 1997 irrigated crops. Overall, the highest seed yields were obtained under irrigated conditions when crops were mown during early growth or at early flowering. The potential seed yield of alfalfa varieties is sufficient to guarantee a profitable seed harvest. However, the harvest efficiency of the combine-harvester was low (20% of the potential seed yield); thus, more appropriate harvest techniques should be used.     

Effects of irrigation and harvest management on dry-matter yield and seed yield of annual clovers grown in pure stand and in mixtures with graminaceous species in a Mediterranean environment

Forage crops in Mediterranean environments are characterized by variable seed and forage production. Knowledge of the effects of agronomic factors on annual clovers grown in pure stand and in association with grasses is essential for their effective exploitation of the available environmental resources. Herbage and seed production were evaluated in southern Italy in an experiment with winter annual forage crops during the years 1992–95. Clovers (Trifolium alexandrinum L., berseem; T. incarnatum L., crimson; T. resupinatum L., Persian; and T. squarrosum L., squarrosum) and graminaceous forage crops (Hordeum vulgare L., barley; and Lolium multiflorum Lam., Italian ryegrass) were used to examine the agronomic effects of irrigation and harvest management. The clovers were evaluated in pure stand and in mixture, whereas the graminaceous species were evaluated only in mixtures. The mixtures were sown in alternating, equally spaced rows. The parameters evaluated were forage dry-matter yield, seed yield and its components. The results showed wide differences in forage production between clovers in pure stands and in binary mixtures. Mean dry-matter production from forage harvest of pure stands of irrigated clovers taken when 10–15% of the stems were flowering yielded 4·36 t ha^–1, that is 0·67 and 0·55 of that of irrigated mixtures of clovers with either Italian ryegrass or barley, respectively, harvested when 10–20% of the graminaceous components were at the heading stage. The forage yield of non-irrigated pure stands of clovers was 0·60 of that of irrigated plots, whereas non-irrigated mixtures yielded 0·82 and 0·86 of that the irrigated treatments for Italian ryegrass or barley mixtures. The mean seed yield of non-irrigated pure stands of the clovers was 0·51 of that of irrigated stands, which yielded 451 kg ha^?1. Persian clover gave the highest seed yields (732 kg ha^?1 under irrigation). These higher yields were related to a higher number of fructiferous organs per stem in Persian clover. When a forage harvest had previously been taken on irrigated clover plots, the subsequent mean seed yields were greatly reduced to 0·76 for berseem and 0·21 for Persian clover and were almost negligible for crimson and squarrosum clover. When irrigated and grown in mixtures with Italian ryegrass, only berseem produced a worthwhile yield of 0·36 compared with that of pure clover taken for seed without a forage harvest; mixtures with barley gave yields of 0·71, 1·07 and 0·20 for berseem, crimson and Persian clovers, respectively, compared with seed yield from uncut pure clover.     

White clover seed production from mixed swards: effect of sheep grazing on stolon density and on seed yield components of two contrasting white clover varieties

A trial was carried out over two harvest years to assess the effect of sheep grazing and closing date on stolon density and seed yield components of two contrasting white clover varieties and to determine the potential for producing clover seed from mixed swards in an integrated livestock/seed production system.
Overall, the small-leaved cv. S184 had a higher stolon density at closing and harvest than the large-leaved cv. Olwen, but only significantly so in 1987. Stolon density at closing was generally increased by delaying closing. Varieties also differed in their response to closing date. Stolon density of cv. S184 in both harvest years, generally increased with later closing whilst cv. Olwen was less influenced by closing date and at all dates in 1987, and all but one date in 1986 was not significantly different from the ungrazed treatment.
Delay of closing significantly increased stolon density at harvest on all closing dates in 1987 but had no effect in 1986. Varieties responded similarly to a delay in closing but the magnitude of increase of cv. Olwen was less than that of cv. S184.
The seed yield components of both cv. S184 and cv. Olwen were influenced by closing date, but the effect differed between years. Although there was some initial increase in inflorescence production, delaying closing after inflorescence buds appeared on the stolon reduced inflorescence number of cv. Olwen in both years but reduced inflorescence number in cv. S184 in 1986 only. However, inflorescence size, seed yield per inflorescence and the proportion of ripe inflorescences at harvest was reduced in both years. Cultivar S184 produced more inflorescences than cv. Olwen in both years and in both years tolerated later closing than cv. Olwen.
The effect of sheep grazing and closing date is discussed in relation to stolon removal and the suitability of particular leaf types for this system of seed production.